dowty



Feb. 25, 1941. G. H. DOWTY AIRCRAFT UNDERCARRIAGE Original Filed Nov.20, 1953. E Sheets-Sheet l Feb. 25, 1941. DQWTY I R. 21,724

AIRCRAFT UNDEHCARRIAGE Original Filed Nov. 20, 1935 2 Sheets-Sheet 2 INVE/V 7' O e 61H. Dowi'y.

Reissued Feb. 25, 1941 UNITED, STATES PATENT OFFICE Original No.2,049,109, dated July 28, 1936, Serial No. 50,784, November 20, 1935.Application for reissue July 30, 1937, Serial No.

Great Britain July 2, 1934 26 Claims.

This invention relates to aircraft undercarriages of the retractabletype, or to tailwheels of like type, in which the wheels (or floats orskids) and their associated structure are adapted to be 6retractedtowards or into the wings or fuselage, or points adjacentthereto. A primary object of the present invention is the provision oflifting means in the form of a'self-contained unit attachable to theaeroplane by one or more pins 10 or like fittings. The invention is moreparticularly applicable to that type of undercarriage in which oneelement, for example a strut, is, for the purpose of retraction, adaptedto "break" about an axis of articulation between its ends, so

that its overall length may inefiect shorten. It may be desirable insome cases to provide such an element with means for breaking it orreextending it, which does not require points of anchorage: or ofapplication of force external to 20 the element; and means will for thepurpose of convenience, be referred to as retracting gear, and it maycomprise either a prime mover, or, as

is preferred in the present case, some form of slave unit such a jacksystem, or a mechanism 5 adapted to be driven by an external source ofpower, by transmission which will be substantially unaffected by themovement of the element. A

further object of the present invention is the,

provision of hydraulic -means for retracting un- 30' dercarriages,adapted to be carried by, and form part of, a strut. Inthe followingdescription the action which is termed breaking is deemed to meanangular movement between two pivotally interconnected or articulatedparts, about a cen- 35 tre which is disposed between their ends orpoints of pivotal attachment to the rest of the'structure.

In effect it means a sort of knuckle joint'action. According to theinvention broadly stated, the retracting gear-is carried wholly by thebreakable 4o element which it is to control, so that no externalmechanism other than the source of energy or controlling gear, isrequired which can be substantially afiected by the movements of theelement. In a preferred form of the invention, as 45 applied to a strutwhich is breakable, the two articulated units consist of two deformabletriangular frames, andfone side of each triangle is variable in length,for example by comprising wholly or in part a hydraulic jack. Further,ac- 60 cording to the invention, a foldable strut for use withretraction gear ior aircraft comprises mutually articulated elements andcarries means for applying moments about the, centre of articulation,the reaction of which means is taken by the 58 strut itself without anyexternal connections being necessary for the moment applying means. Theinvention therefore provides a strut element 1 for retractableundercarriages comprising a structure with pivoted joint or jointsbetween its attached ends, and means carried by the structure forapplying a moment at the joint or joints for controlling the relativeangular position of the articulated parts of the structure. By theemployment of the above features it follows that an undercarriage can beretracted without the neces-' 10 sity for additional points ofattachment, and without resort to means external to a foldable strut,except, perhaps, the provision of a prime mover or source of energysuitably connected. The invention also includes a construction of strutII for retractable aircraft undercarriages in unit form, as will bedescribed hereafter. The inventlon includes the use of purely mechanicaljack retracting gear, driven from an external source, and tarrangedaccording to the foregoing statemen- A preferred form of the inventionis illustrated diagrammatically in the accompanying drawings, in which:

Figure 1 is a side elevation of the improved strut, parts being brokenaway and shown in section; and

Figure 2 is a diagrammatic side elevation of the strut in a brokenposition.

In these figures the strut comprises two shelllike members or sections Iand 2 of substantially triangular form" adapted to meet on a common baseline at 3. Towards the aplces of these memhers, I and 2 are fittings IAand 2A adapted to be pivotally connected one to a suitable pin iit- 36ting on the aircraft, and the other to the axle or other lower part ofan undercarriage to be retracted. The elements i and 2 are pivotallyjoined together by a pin or bolt 4 at the axis about which breaking isrequired. The bolt 4 40 also carries pivotally a bracket fitting 5 whichis again of triangular form, The fitting 5 houses certain partshereinafter described. Towards the outer ends of the elements I and 2there are provided pins 6 and I. It is unnecessary to reduplicate thedescription, so the following describes the parts appropriate to themember I;' the pin 8 carries with slight angular freedom the end fittingIi which forms a cap for a hydraulic jack cylinder 9 in which thereoperates a jack piston III with a piston rod protruding through theother ends of the cylinder 8, with a suitable slide packing ii. In thecap member 8 there are two pipe connections BA and 8B for the admissionand emission of operative fluid under suitable control. The piston IIIis a double-acting piston, and

the lower end of the cylinder 9 has an inlet passage at I3 connecting itwith a pressure pipe II. The precise nature of the hydraulic arrangementmay be suitably varied and forms no part of the invention, but it may bementioned that since an identical hydraulic jack is provided in theelement 2 also, the pipelines such as It are suitably connected up withany necessary intermediate lengths of flexible pipe such as indicated atI5,

to accommodate breaking of the strut and to allow the slight angularmovements of the cylinder 9 for example about the pin 8. Ordinarily itis presumed that the two jacks are identical, andtheir'connections aresimple parallel connections. The outwardly projecting end of the pistonrod II carries a fork fitting I6 carrying in turn a suitably journalledpinion I! on an axis in the form of a pin HA. The pinion I1 .is rigidwith the fork I6, but the fork and pinion are angularly movable aboutthe pin "A, which supports them in the fitting 5. The pinion Ilconstantly meshes with an idle pinion I8, also carried rotatably by thebracket 5; pinion I8 in turn meshes with the like pinion I9, and thepinion I9 finally meshes with a pinion 20 which is attached to theexternal end of the piston rod 2I belonging to the other, hydraulicjack, the cylinder of which is shown at 22. By virtue of this train ofpinions it follows that any anguiarmovemen-t of the Jack comprising thecylinder 9 and the rod I I with I respect to the fitting 5, necessarilyentails like but opposite angular movement of the jack comprising thecylinder 22 and rod 2|. Consequently any slight failure of one jackhydraulically, or lag as between one jack and the other, can becorrected by this positive train of engagement. I It will be observedthat on each side of the common base 3 a triangular structure ispresent; for example, in the element I there is a stress trianglecomprising the hydraulic jack as a whole, connecting the axes at 6 and"A, the fitting 5 connecting the axis at "A to the axis at l, and themember I itself connecting the axis at 4 to the axis at 6. When theradius rod is fully extended as shown in Figure 1, it may be providedthat the contacting edges at 3 of the shell parts I and 2 provide asuflicient abutment to take all compression loads between the fittingsIA and 2A, but if this is not convenient, the compression loads may beshared by the members of the triangle above described and thecorresponding triangle in the element 2; this is especially so if (asshown in Figure 1) the parts 8, II) come into mechanical abutment,whereby compression loads are transmitted through the trianglespositively, and there need be no hydraulic pressure.

Figure 2 shows how the construction above described efl'ects retraction.If liquid under pressure be introduced for example, through the ,union8A (and of course the corresponding union into cylinder 22) the pistonrods forced outward from the cylinders, consequently applying a momentabout the'axis at 4, and it will be observed that there is no reactionexternal to the radius rod as a whole, in that the cylinder 9 acts onthe pin at 6 and the rod ll acts on the pin at mi. when this takes,place the side of the triangle i/IIA is elongated and therefore themember I moves angularly'about the axis 4;

- simultaneously of course the member 2 moves symmetrically in oppositesense about the same axis, and the result of such movement is a'positionshown for example as in Figure 2. The de- IIand 2| are,

crease in distance between the fittings IA and 2A so that theconstruction returns to the position as shown in Figure l.

Usually, when the-strut is extended as in Figure ,1, its ex-temalelements I and 2 will take the whole of the longitudinal stressesin it,but it may be arranged that these loads be shared, or taken wholly,through the jacks themselves.

In an alternative construction, not illustrated, only one jack isprovided and employed, of which the cylinder is pivotally attached tothe element I and the piston to the element 2, so that extension orcontraction of this single jack produces articulate movement of theradius rod; the thrust line of the jack is for this purpose ofiset fromthe axis of articulation. Again, if it is not desired to harmonize theaction of the two jacks above described positively, the train of pinionsI1, I8, I9 and 20 maybe omitted. In any case, however, it will beobserved that the self-contained retracting gear of the radius rodapplies moments for breaking it about its centre of articulation.

lated parts thereof, that is to say the parts I and 2 as abovedescribed.

What I claim as my invention is:

1. A strut comprising companion sections, a bracket between adjoiningends of said sections housed by the sections when the sections are inalinement, a pin pivotally connecting both sections with said bracket,and adjusting means for said sections consisting of cylinders extendinglongitudinally in said sections, pistons working in said cylinders androds extending from said pistons out of the cylinders and pivoted tosaid bracket in ofl'set relation to the pivotal connection of thesections with the bracket.

2. A strut comprising companion sections, a bracket between adjoiningends of said sections pivoted to the sections and having end portionsextending into the sections when the sections are in axial alinementwith each other, a cylinder extending longitudinally in each section andtiltable transversely of the'sectlon, and pistons slidablelongitudinally in said cylinders having rods extending from thecylinders of said bracket.

and pivoted to ends" 3. A strut comprising companion sections, a

bracket between adjoining ends of said sections pivoted to ends of thesections and having end portions projecting into the sections when thesections are in axial alinement with each other,

a cylinder extending longitudinally in each section and mounted fortilting movement transversely of the section, a piston slidablelongitudinally in each cylinder, rods extending from said.

pistons through ends of said cylinders and pivoted to ends of saidbracket; and means for transmitting swinging movement from one pistonand 7 sections are in axial alinement with each other. 0

a cylinder extending longitudinally in each section and mounted fortilting movement transversely of the section, a piston slidablelongitudinally in each cylinder, rods extending from said pistonsthrough ends of the cylinders towards said bracket, pinions rotatablycarried by ends of said bracket, the piston rods being secured to saidpinions and extending radially therefrom, and idler pinions rotatablycarried by said bracket and meshing with the first mentioned pinions andeach-other.

.5. In an airplane undercarriage, a pair of sections having adjoininginner ends, a mounting for said sections having inner ends of thesections pivoted thereto intermediate ends of the mounting, cylindersextending longitudinally of said sections and having their outer endspivoted to the sections for movement transversely thereof, pistonsslidable in said cylinders and having rods projecting from inner ends ofthe cylinders, fluid pressure connections for said cylinders, and meanspivotally connecting thepiston rods with the ends of said mounting inolfset relation to the pivotal connection between the mounting and theinner ends of the cylinders, said piston rods being shiftable by fluidpressure flowing through said connections into the cylinders forshifting the sections with respect to each other.

6. A. strut comprising companion sections having inner ends adjacenteach other, a mounting pivotally connected intermediate its length toinner ends of the sections, and adjusting means for said sectionsconsisting of cylinders extending longitudinally of the sections andhaving their outer ends pivotally connected with the sections, andpistons slidable in said cylinders and having rods extending from innerends of the cylinders and pivoted to ends of said mountings in oflsetrelation to opposite sides of the plane of the pivotal connection of thesections with the-mounting.

7. A strut comprising companion sections,- a

mounting between adjoining ends of the sections pivoted intermediateits'length to ends of the sections, and a hydraulic jack including'acylinder extending longitudinally of each section, a piston slidablelongitudinally in each cylinder and having a rod extending from one endof the cylinder, one end of the hydraulic jack being pivotally connectedto the section and the other end being pivotally connected to-themounting in offset relation to opposite sides of the plane of thepivotal connection of the sections with the mounting.

8. A strut comprising two companion sections formed to engage each theother when alined, whereby to be self-resistant to compression loadbetween their.remote ends, a pivot joint joining adjacent ends of saidsections, pivot joints at the remote ends of said sections for attachingthe strut to aircraft parts, and jack means, wholly carried by thestrut, for causing relative angular movement of said sections. 1

9. An aircraft strut for connecting two relatively movable parts of anaircraft structure, comprising two articulated sections adapted forconnection at two points, one at one end of the strut to one such partof the aircraft structure, and the other at the remote end of the strutto the secondpart of the aircraft structure, said points of connectionbeing so located that a line joining them, when the sections are alined,passes to one side of the axis of articulation, means carried whollyupon the strut, reacting from one sections.

section to the other, to break the strut, and to swing the points ofconnection to the opposite side of the axis of articulation, or toreturn the sections to alinement' from such broken position, and meansmovable with each section, formed and proportioned to contact with thecorresponding means movable with the other section, when the sectionsare alined, to positively transmit thrust from one section to another,without reliance on the strut-breaking means.

10. A strut comprising two sections pivotally connected and relativelymovable about such pivotinto and from alinement, and formed forconnection at their respective swinging ends to two relatively movableparts of an aircraft structure, means carried wholly by such strut foreffecting such swinging movement of the sections, and two cooperatingthrust-transmitting means, one movable with one section and the otherwith the other section, formed to contact when the sections are inalinement, thereby to constitute the primary means to transmitcompression loads from one such aircraft part to the other.

11. An aircraft strut comprising two relatively movable sections eachadapted for connection at a. single point to one of two aircraft partswhich are relatively movable to effect movement of such points along aline towards and from each other, means guiding the sections forrelative movement which has a component transversely of such line, andmeans carried wholly by the strut for I so moving the sections.

12. An aircraft strut comprising two hollow shells of generallytriangular form in elevation, a pivot pin connecting said shells at oneangle for relative swinging movement towards and from alinement, eachshell being formed, at its swinging end, for connection to an aircraftpart, and power means enclosed wholly within a shell, and

, reacting from the other shell, for effecting relative swingingmovement of the shells.

13. In a retractable aircraft undercarriage, the combination of agenerally hollow structural component adapted to break about an axis ofarticulation between its ends, and retracting means disposed within saidhollow component so as to produce reaction between the articulated partsthereof, and to produce a breaking moment about said axis. l

14. For retractable undercarriages for aircraft, a hollow strutcomprising in combination articulated sections, each section comprisinga deformable triangular frame,. and such frames of the two sectionshaving one side in common, and a Jack enclosed within the hol-, lowstrut and forming another side of each such triangle, whereby suchtriangle is deformable to produce articulated movement of the sectionsof the strut.

, 15. An aircraft strut comprising two sections which are substantiallytriangular in elevation, a pivot pin connecting the two sections at anacute angle of each, for relative swinging movement to and from analined position, wherein their bases adjoin and a line connecting theirapices intersects'the bases, said sections, at their apices, beingformed for connection respectively to one of two relatively approachableaircraft parts, and means carried wholly by the strut for effecting suchrelative swinging movement of the 16. An aircraft strut comprising twosections which are substantially triangular in elevation,

acute angle between the base and a side of each,

"for relative swinging movement to and from an alined position, whereina line-connecting their apices intersects their bases, and their basescontact to transmit compression loads from one apex to the other alongsuch line, said sections, at

' parts, the axis of articulation being located, when the sections arealined, at one side of a line of thrust connecting said ends, hydraulicjack means 7 carried wholly by, said strut to break the same,

and thereby to move the ends so thata line connecting them lies'on theopposite side of such axis, said jack means including two relativelymovable elements so formed as to contact each other, when the sectionsare alined, thereby to constitute positive thrust-transmitting elementsin such position of parts.

18. An aircraft strut including two sections,

and formed at its opposite ends for pivotal connection to two relativelymovable aircraft parts, and a pivot pin connecting the two sections anddisposed parallel to one of the terminal pivotal connections, and meanscarried wholly by the strut, and reacting between the sections, toproduce amoment about said pivot pin, thereby to effect approach of thetwo terminal pivotal connections.

19. An aircraftv strut comprising two pivotally connected terminalelements and an intermedi-,

ate element, the two terminal elements, when in normal position, beingsubstantially alined to transmit forces from the outer end of one to theouter end of the other, and means reacting from the intermediate elementand between the two terminal elements to produce a torque about theirpivotal connection, thereby to effect approach of such outer ends of theterminal elements, and to lessen the effective length of the strut as awhole.

20. An aircraft strut comprising two terminal elements and anintermediate element, the two terminal elements, when in normalposition,being substantially alined to transmit forces from the outer end of oneto the 'outer end of the other, and means reacting from the intermediateelement, in a direction transverse to the strut as a whole, to effectapproach of such outer ends of the terminal elements, thereby to lessenthe effective length of the strut as a whole.

21. An aircraft strut comprising twoterminal elements and anintermediate element, the two terminal elements, when in normalposition, being substantially alined to transmit forces from the outerend of one to the outer end of the other, and means carried wholly byone of the terminal elements and reacting from the intermediate "elementto eifect approach of such outer ends of the terminal elements, therebyto lessen the effective length of the strut as a whole.

22. An aircraft strut comprising two terminal elements and anintermediate element, the two terminal elements, when in normalposition, be-

ing substantially alined to transmit forces from the outer end of one tothe outer end of the other, and means carried wholly by each of theterminal elements, and reacting from the intermediate element to effectapproach of the outer ends of the terminal elements, thereby to lessenthe effective length of the strut as a whole.

23. An aircraft strut, to effect approach or recession of two relativelymovable aircraft elements by lessening or increasing, respectively, the

effective length of such strut, comprising two articulated sectionspivotally connected to each other, each by an end, a pivot connectionformed at the remote end of each section, for seourement to one of suchaircraft elements, and force-producing means carried wholly by thestrut, and organized and arranged to react only between the twosections, to produce amoment about the axis of articulation, and therebyto move the sections from a position of substantial alignment to afolded position, orvice versa.

24. An aircraft strut, for connectingan aircraft fuselage or the likeanda relatively movable undercarriage, comprising two parts pivotallyconnected intermediate the ends of the strut as a whole, and a pinfitting carried by each such part for interconnection to a complementalfitting on the aircraft structure and undercarriage, respectively, andconstituting the sole supporting connection of the strut thereto, meanscarried wholly by the strut to exert a torque about the pivotalinterconnection between the two parts, and distant means on.the aircraftstructure for the oontrol'of the preceding means.

25. An airplane landing gear strut, comprising two companion sections, apivot joint joining adjac'ent ends of said sections for relative pivotalto said pivot joint at the remote end of each I section, constitutingthe sole means for attackment of the strut to relatively movableaircraft parts, hydraulic jack means wholly carried by the strut andreacting solely between. the two sections, for causing relative angularmovement of said sections about said pivot joint, and consequentrotation of each section about its terminal pin, and a pressure line forconnecting the jack means to a distant pressure source, and constitutingthe sole jack-operating means which extends exteriorly of the strut.

GEORGE HERBERT DOWTY.

